Current developmental policy reports and empirical articles stress the importance of supporting Spanish (L1) in English-dominant (L2) child care programs as well as promoting the linguistic context in which Dual Language Learners (DLLs) are served. Yet, little is known whether teachers actually use L1 in early care and education (ECE) settings and for what purposes, and prior research has not sufficiently investigated whether the effects of Head Start vary based on such L1 use. This mixed-methods study addresses several kindergarten-readiness topics of interest to the Child Care Development Fund (CCDF). Specifically, the study first seeks to understand the role of linguistic cohesion between staff and Spanish-speaking DLL families to answer: 1) What child, family, and institutional factors are associated with selection into ECE environments that use L1?; and 2) a) Are there main effects of L1 use on academic school readiness skills? b) Does Head Start differentially benefit children spoken to in L1 and/or instructed in L1? To address these research questions, two nationally representative samples of Head Start children, families, and programs - the Head Start Impact Study (HSIS) and the Head Start Family and Child Experiences Survey (FACES, 2009 Cohort) - will be analyzed. Using the results from these secondary data analyses on the role of L1 use in ECE for children's academic skills, classroom observations will then be conducted in local Orange County, CA Head Start centers to better understand the nuanced mechanisms and patterns surrounding such L1 use to answer: 3) How is L1 used in local Head Start classrooms, who uses it, for what purposes, and how does L1 contribute to children's active engagement? Sample: ? Spanish-speaking DLLs from HSIS (N = 1,141) and FACES-2009 (N = 512) study samples ? Orange County Head Start classrooms in which Spanish-speaking DLLs interact with lead teachers, assistant teachers, aides, parent volunteers, and other children (N ? 3,400). Measures: Spanish-speaking DLL Status ? The HSIS (baseline Fall 2002 child's primary caregiver and child)and FACES-2009 (Baseline Fall 2009 & Spring 2010 child language screener) datasets L1 Use ? Child's teacher/caregiver from the HSIS (Spring2003) and FACES-2009 (Spring 2010) datasets Academic Achievement Baseline ? Woodcock-Muoz (WM) Identificacin de letras y palabras (Woodcock & Muoz-Sandoval, 1996) ? WM Problemas aplicados ? Test de Vocabulario en Imgenes Peabody (TVIP; Dunn, Lugo, Padilla, & Dunn, 1986) Academic Achievement Outcomes ? Woodcock-Johnson (WJ) III Letter-Word Identification (Woodcock, McGrew, & Mather, 2001) ? WJ III Applied Problems ? HSIS: Peabody Picture Vocabulary Test (PPVT), 3rd Ed. (Dunn & Dunn, 1997) FACES-2009: PPVT, 4th Ed. (Dunn & Dunn, 2007) Selection Variables ? Maternal Proficiency with English ? Lead Teacher Speaks L1 ? Lead Teacher of Hispanic Ethnicity ? % of Spanish-speaking DLL Students Per Center ? Maternal Immigration Status ? Child's Previous ECE Experiences ? Availability of Other ECE Options Demographic Covariates ? Child Gender ? Child Classified as Special Needs ? Child Age (weeks) ? Child Age (years) ? Maternal Depression ? Highest Level of Maternal Education ? Whether Both Biological Parents Live with Child ? Maternal Marital Status ? Whether Mother was Teenaged at Child's Birth